Rising temperatures can facilitate epizootic outbreaks, but disease outbreaks may
be suppressed if temperatures increase beyond the optimum of the pathogens while still
within the temperature range that allows for effective immune function in hosts. The
two most devastating pathogens of wild amphibians, Batrachochytrium dendrobatidis
(Bd) and ranaviruses (Rv), co‐occur
in large areas, yet little is known about the consequences of their co‐infection and
how these consequences depend on temperature. Here we tested how exposure to Bd
and subsequent exposure to Rv, followed by treatment at
elevated temperatures (28 and 30°C versus 22°C) affected Bd
and Rv prevalence, infection intensities, and resulting
mortalities in larval agile frogs and common toads. We found multiple pieces of evidence
that the presence of one pathogen influenced the prevalence and/or infection intensity
of the other pathogen in both species, depending on temperature and initial Rv
concentration. Generally, the 30°C treatment lowered the prevalence and infection
intensity of both pathogens and, in agile frogs, this was mirrored by higher survival.
These results suggest that if temperatures naturally increase or are artificially
elevated beyond what is ideal for both Bd and Rv,
amphibians may be able to control infections and survive even the simultaneous presence
of their most dangerous pathogenic enemies.
